Phase Formation of a Solid-Liquid Mn–Ga Diffusion Couple under a Magnetic Field

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In-field heat treatments of an Mn–Ga diffusion couple were performed at 773 K for 12, 24 and 48 h to investigate the phase formation under magnetic fields. Formation of the MnGa₃, Mn₂Ga₅, MnGa, Mn₃Ga₂ and β-Mn phases was confirmed for magnetic fields of 0 T and 5 T. For a diffusion-controlled process, there is a parabolic relationship between the thickness of the phase layers and annealing time for the MnGa and Mn₂Ga₅ phases. The parabolic coefficients of MnGa and Mn₂Ga₅ for a zero magnetic field were determined as 8.7 × 10⁻³ µm²s⁻¹ and 4.6 × 10⁻¹ µm²s⁻¹ respectively. For a magnetic field of 5 T, the parabolic coefficients were evaluated as 11 × 10⁻³ µm²s⁻¹ for the MnGa phase and 4.5 × 10⁻¹ µm²s⁻¹ for the Mn₂Ga₅ phase.

Fig. 4 Average thickness of the MnGa and Mn₂Ga₅ phase layers as a function of the square root of annealing time with and without μ₀H = 5 T. The solid and broken lines represent the least-squares fits to the data of μ₀H = 0 T and 5 T, respectively.